Diesel fuel is a refined petroleum product that is burned in the engines powering most of the world's trains, ships, automobiles and trucks. Petroleum is of course, a non renewable resource of finite supply. Acute shortage and dramatic price increases in petroleum and refined products derived from petroleum have caused great burden on consumers during the past quarter century. Further, diesel engines emits relatively high level of pollutants, especially particulates such as inter alia soot, adsorbed hydrocarbons and sulfates, which are usually formed due to incomplete combustion of fuel and is responsible for serious health hazards. The others most common pollutants in diesel exhausts are nitric oxides and nitrogen oxides, hydrocarbon and sulfur dioxide, and to a lesser extent, carbon monoxide. Accordingly, extensive research effort is now being directed towards replacing some or all petroleum based diesel fuel with a cleaner-burning fuel derived from sustainable sources such as non-edible oils.
The vegetables oils have comparable energy, density, cetane number, heat of vaporization, and stoichiometric air/fuel ratio with mineral diesel. In addition, they are biodegradable, non-toxic, and induced significantly less pollution. The use of vegetable oils and their derivatives in diesel engines leads to substantial reductions in emission of sulfur oxides, carbon monoxide, poly-aromatic hydrocarbons, smoke, particulate matters and noise. Furthermore, the contribution of bio-fuels to green house effect is insignificant. The vegetable oil is often directly added to diesel fuel to operate compression ignition engines and is an attempt to replace at least a portion of the diesel fuel. These vegetable/non-vegetable oils are composed mainly of triglycerides, and often contain small amounts (typically between 1 to 10% by weight) of free fatty acids. But due to worldwide shortage of edible food products, their use to supplement diesel fuel is discouraged. The researchers now focus on the use of non-edible oil, like Jatropha and rapeseed oil.
Jatropha is non-edible oil being singled out for large-scale plantation. This plant can thrive under adverse conditions. It is drought-resistant, perennial plant, living up to fifty years and has the capability to grow on marginal soils. It requires very little irrigation and grows in all type of soils. The production of Jatropha seeds is about 0.8 kg per square meter per year. The oil content of Jatropha seed ranges from 30 to 40% by weight and the kernel itself ranges from 45% to 60%. The fatty acids composition of Jatropha is mainly of linoleic or oleic acid type, which are unsaturated fatty acids. The fatty acid composition of Jatropha oil consists of myristic, palmitic, stearic, arachidic, oleic and linoleic acids. The oil compares well against other vegetable oils and more importantly to diesel in terms of its fuel rating per kilogram or hectare of oil produced.
Consequently there remains a need for an improved fuel derived from non-edible oil sources that can be used either alone as blended with petroleum-based diesel fuel.
It is therefore an objective of the instant invention to provide an alternative fuel source that does not contains fatty acids methyl esters.
It is a further objective of the instant invention to provide an alternate fuel source that can be used on existing engines without needing to modify or retune the engines.
It is still further objective of the instant invention to provide a fuel additive that, when combined with diesel fuel, does not adversely affect the engine in the long-term use.
It is yet another objective of the instant invention to provide a bio-fuel with additive that, when used in the system will not generate NOxs and SOxs, and consequently it will provide a cleaner source of alternate fuel.
It is still another objective of the instant invention to provide a fuel free from soap and other by-products.
It is still further objective of the instant invention to provide a process that does not require any outside energy to accomplish the production of bio-fuel.
It is yet still further objective of the instant invention to provide a material, which when it is part of the fuel, will reduce carbon emissions, thus eliminating the need of adding smoke or emissions suppressants.
Diesel fuels are known to contain a synergistic cetane improving additive combination of peroxidic component and an aliphatic polyether of the formula R(—O—X)n O—R@1 where R and R@1 are alkyl groups, X is an alkylene group and n is an integer (U.S. Pat. No. 2,655,440 and divisional U.S. Pat. No. 2,763,537.
European Application 80-100827.7 describes the use of various propylene glycol mono-an-di-ethers as a component of diesel fuels. The composition mono-an-di-ethers is also sued as a component of diesel fuel. The compositions described in this reference involve a multi-component formulation, which includes poly-ethers, acetals, lower alkanols, water and only up to 85 volume % diesel fuel hydrocarbon.
The UK Patent 1246853 describes the addition of dialkyl ethers of propylene glycol as smoke suppressants in diesel fuel.
The U.S. Pat. No. 4,753,661 describes a fuel such as diesel fuel containing a conditioner, which comprises a polar oxygenated hydrocarbon, a compatibilizing agent, which is an alcohol, aromatics, and a hydrophilic separant which may be a glycol monoether.
The Japanese patent 59-232176 describes the use of di-ethers of various polyoxyalkylene compounds as diesel fuel additives.
The addition of glycol ethers and metallic smoke suppressants has been found to reduce the smoke and soot emissions. These suppressants have been found to reduce smoke and soot emissions. These metallic smoke suppressants are typically metal salts of alkanoic acids (U.S. Pat. Nos. 3,594,138, 3,594,140, 3,615,292 and 3,577,228). The health and environmental risks of barium are major concerns in these instances.
The European Application 82-109-2665 describes the use of ethers to reduce soot. However, a number of these ethers are unable to be used commercially in the US because the resulting fuel does not meet the flash point specification of 126° F. This application also teaches that glycol ethers are not highly effective at reducing exhaust emissions. The Japanese Patent Application 59-232176 teaches that glycol ethers of the formula R1—O—(CHR2—CH2—O—)nR3, where n is less than five have the effect of reducing particulates. The CO and HC emissions are reduced.
Winsor and Bennethum (SAE 912325) describe the use of ether diglyme to reduce particulate emissions. In addition to being costly to produce, diglyme is highly toxic and has been associated with increased rates of miscarriages. Glycol ethers based on the higher alkylene oxides, especially propylene and butylenes, are far less toxic than those based on ethylene oxide. Glycol ethers based on ethylene oxide also have unfavorable water partition coefficients. The water partition coefficient for diglyme is greater than 17 eliminating this as a choice for commercial use as a diesel fuel additive.
The addition of dialkyl carbonates and dialkyl dicarbonates, particularly dimethyl carbonates to diesel fuel has been described to reduce exhaust emissions from compression ignition engines (U.S. Pat. Nos. 32,311,386, 4,891,049, 5,004,480, and 4,904,279). The high volatility of the lower alkyl carbonates prevents their addition in substantial amounts to typical D-2 diesel fuel. While some dicarbonates have lower volatilities, their poor hydrolytic stability precludes their commercial use.
Environmental regulations worldwide have established certain emission standards for diesel engines, particularly with regard to nitrogen oxide and particulate matter emissions. The contribution of diesel fuel sulfur content to exhaust particulates has been well established, and has led to an EPA regulation requiring highway diesel fuels to contain no more than 0.05 wt % sulfur and the particulate matter emissions to drop from 0.60 to 0.25 grams/BHP-hr. Similarly, allowed nitrogen oxide has been decreased from 6.0 to 4.0 grams/BHP-hr.
Many strategies are used by the industry to reduce exhaust emissions. Improved heavy diesel engines designs including higher injection pressures, turbo-charging, air inter-cooling, retarded injection timing through electronic tuning control, exhaust gas recycle and exhaust after treatment devices are some examples of the attempts to lower environment emissions. However, for these advanced technologies to work, a high quality, low emissions diesel fuel is required in addition to the use of various fuel additive improvements such as cetane and diesel fuel detergents to keep fuel injectors clean and improve the performance of low ash engines oils. A combination of these strategies will have to be utilized to meet newer clean air standards worldwide. The key focus is to find the most effective combination of technologies which offer the best cost/performance.
The instant invention overcomes all of the diesel fuel problems by introducing a state of the art nano material which, when incorporated in the diesel fuel considerably reduces the formation of sulfur and nitrous compounds as well as hydrocarbons, carbon monoxides and unregulated aldehydes emissions.
Simple and polymeric esters are major products of the chemical industry. There are a wide variety of processes available for their production including direct esterification by reactions of alcohols with carboxylic acids or anhydrides as well as various interchange reactions including alcoholysis, in which the alcohol moiety of an ester is exchanged by another alcohol, acidolysis, and transesterification in which the alcohol moieties of two different esters exchange with each other. In the absence of a catalyst, esterification and transesterification reactions tend to be quite slow and result in the formation of byproducts, which require additional steps for their conversion. For this reason, reactions are almost always catalyzed. Acids, bases, and transition metal based catalysts are widely used in various applications. However, there are a number of problems associated with the use of acidic and basic catalysts. These catalysts often promote undesirable side reactions which can make it difficult to isolate a pure product without employing extensive purification procedures. Furthermore, they also often require neutralization at the end of the reaction as well as removal from the product. This again requires addition of extensive purification process or the use of another process step. The whole process then becomes economically unfeasible for commercialization.
To avoid many of the problems associated with acidic or basic catalysts, two types of catalysts are used (i) heterogeneous (ii) homogeneous. Homogeneous catalysts are soluble in reaction medium and for this reason they suffer from one of the major problems associated with many acidic and basic catalysts, i.e., the removal of the catalyst at the end of the reaction, which turns out difficult, if not impossible. Often even trace amounts of metal impurities in products are intolerable and, therefore, complex steps are needed to reduce metal contents to acceptable levels. This results in additional processing steps, waste, and/or yield losses. Further more, homogeneous catalysts are often destroyed during removal. This “once-through” utilization of the catalyst can result in unacceptable high manufacturing cost.
Heterogeneous catalysts are relatively insoluble in reaction medium. As a result, they avoid many of the purification problems associated with acidic, basic, and homogeneous catalysts. Often they can be removed from the product by a simple filtration step. However, since their activity occurs at the catalyst surface, rather than in solution, heterogeneous catalysts tend to have low activity. Thus the goal of catalyst research is to discover heterogeneous catalysts, which are not only selective and easily removed from the reaction mixture, and also become part of the fuel and thus contribute towards the enhancement of its properties.
The U.S. Pat. No. 4,043,941 and No. 4,032,550 describe the preparation of heterogeneous transesterification catalysts with high activity and good stability of these free-flowing powders. Although the catalyst described in above patents would be considered generally of high activity, they do not contribute in the reduction of particulates and other emissions. Hence a need still exists for highly active heterogeneous transesterifation catalysts that will have shorter reaction time and reduced emissions.
In summary, there are multiple operating options available for making biodiesels. Many of these technologies can be combined under various conditions and feed stocks in a large number of ways. The choice of technology is a function of desired capacity, feedstock type and quality, alcohol recovery, and catalyst recovery. The dominant factor in bio-diesel production is the feed stock cost, with capital cost contributing only about 7% of the final product cost.
It should be further apparent that even in view of known prior art, there remains a need for a procedure and a material which enables the use of crude glycerol, (produced as a byproduct of a biodiesel fuel producing esterification of renewable triglycerides procedure), yielding biodiesels as close in physical property to petroleum-based diesel product in its pour point, viscosity and cloud point temperature, at a very low cost.
There are three non-ester side streams that must be treated as a part of the overall biodiesel process. These are:                1. The excess alcohol that is recycled within the process.        2. The glycerol by product, and;        3. The waste stream from the process.        
These extra steps in the production of biodiesel increase the cost and the length of the process. To minimize these processes, control the cost and to make it more environment-friendly, the instant invention reports a transesterification nano titanium dioxide anatase form of catalyst with high activity, less reaction time and emissions and significantly reduced particulates in the environment.
The use of heterogeneous nano-catalysts is in general new to this field of research. However, it does not seem possible in any industrial process to obtain both the ester and glycerin economically. The use of nano-catalyst of the instant invention makes it possible that no glycerin is formed and the conversion is around 90-95%.
Among the prior art that deals with heterogeneous catalysts, it is possible to cite European Patent EP-B-0 198243 where the transesterification catalyst, which transforms oil and methanol into methyl ester, is an alumina or mixture of alumina and ferrous oxide. In this art, the column that is used for the fixed bed has a volume of 10 liters, and oil is generally injected at a flow rate of less than 1 L/hr, which gives a VVH (volume of injected oil/volume of catalyst/hour) of less than 0.1. For a factory of 100,000 t/year this would correspond to reactors of at least 150 m3. Another problem that arises in this invention is that a substantial amount of glycerin is produced and the purity of ester formed ranges between 93.5% and 98%. What becomes of the glycerin that is not recovered is not indicated. In some cases, it forms glycerin ethers, such as the one that is indicated in this patent; in other cases, it may breakdown, unless it is eliminated in a first stage. The performance evidence provided in this art is low. It is possible to point out that with VVH indicated and contact times of more than 6-hours, conversions of 80% and more can be obtained even without a catalyst. This European patent therefore does not appear to offer a reasonable solution form an economic standpoint.
The UK patent GB-A-795573 describes using zinc silicate as a catalyst at temperature of between 250-280° C. and under a pressure of at least 100 bar, with methanol. It appears that there was 85% conversion in a first stage and 100% if glycerin was decanted in an intermediate step and the reaction was continued.
According to patent EP-B-0-193243, which cites GB-A 795573, zinc soaps would be formed with zinc compounds, which naturally cannot be allowed in the fuel. This is mainly due, it seems, to the high temperature that it is necessary to use in this reaction with this catalyst. In the first stage of the process that is described in this patent, or in the second stage if there are two transesterification stages, the glycerin is diluted, and the ester is washed. In this process, the drawbacks include the requirement of high pressure (more than 100 bar), high temperature (250-280° C.), washing the phases with water and necessary purification of the glycerin is needed to recycle the methanol, to distill it and not evaporate it.
In addition, the U.S. Pat. No. 4,668,439 is known, which describes a continuous production process in which operations are carried out at atmospheric pressure and where the ester and glycerin are evaporated by running excess through oil at more than 210° C., most often 240° C.; in the presence of soluble catalyst, which can be zinc laurate. The only example of zinc compound that is given in this document is, for that matter, the laurate salt; otherwise, the compounds are alkalis and various soaps. All of these examples use soluble catalysts. Glycerin represents only 70% of the theoretical value, which means that there are either losses or decomposition. In this process, the ester and the glycerin are evaporated by the passage of alcohol, which also raises the possibility of only the ester being evaporated and not the monoglycerides, whose boiling point is within a close range. From the energy standpoint in particular, the effectiveness of this process is questionable.
There are other references in the literature that teach use of zinc oxide, but in esterification reactions of glycerin with fatty acids [12]. In the instant invention, it was discovered that there is virtually no difference between zinc chloride, zinc sulfate, zinc powder, barium oxide, potassium bicarbonate, sodium methylate or sodium ethylate, and even lithium hydroxide in terms of their effectiveness. All these salts or oxides that provided yields of between 32 and 39% of monoglyceride in a comparative test when excess glycerin is used.
There are reports that demonstrated that instead of having neutral oil at the start, there is possibility of using acidic oils. This is therefore a first stage whose purpose is to eliminate the acidity of the oil. This reaction is fairly easy because it involves only small percent of the main reaction. In this connection, the zinc aluminate is not considered preferred over zinc in the list of the catalysts if it is desired to avid saponification and/or the formation of zinc salts. Esterification is an easier reaction than transesterification because there is elimination of a reagent; this does not take place in high-temperature transesterification, where as glycerin remains present and soluble.
Finally the prior art does not provide information on a reaction that can be employed economically on an industrial scale for production of bio-diesel.
No patent describes the use of S-doped TiO2 nano-catalyst for the production of bio-diesel and that without producing any side product. This is a breakthrough invention reported here which can be scaled up quite easily and that does not produce any byproducts and demonstrates a very high rate of conversion. In the instant invention, the catalyst becomes the part of the fuel, interestingly reducing NOxs and SOxs formation without changing the over all properties of the produced biodiesel.